Question

im having difficulty understanding why a string supporting a hanging brick just without breaking will break if the brick is then set swinging. i know that this is because there is the addition of the centripetal force but i dont fully understand why? please help

Answer 1

For a given string, there exists 'Breaking tension' i.e the maximum tension the string can bear. Whenever the tension in the string exceeds the breaking tension, the string gets cut.
Now, when the brick is swinging, the centripetal force would add up with the component of weight to give the tension in the string. When the brick is not in motion, only the weight would give you the tension.
So now, you can see that the tension in the string while the brick is swinging is more than that of the tension when the brick is at rest. So there are more chances of the string getting cut when the brick is in motion,

Answer 2

Thanks :) that cleared it up a lot i guess i just got confused because the teacher stared going on about some horizontal force at the bottom as well, i dont know where he got this force from and my tutor didn't either so i dont know what he was on about but what you've said has made sense, thankyou :)

Answer 3

no problem